The Continuation War ran from 1941 through 1944. Soviet offensives in 1944 had essentially fully exhausted Finnish reserves; although Finland had managed to withstand the final one, they judged that they couldn't withstand one more. At that point, the Finns sued for peace (the peace terms being a slightly upgraded (for the Soviets) version of the treaty at the end of the Winter War).
So Russia almost certainly could have rolled into Finland in 1945.
The war hawks here think Russia fully mobilized, Russia which pushed the Wehrmacht back to Berlin in 1945 would have had more than minor difficulty taking over Finland in 1945. Perhaps they should read some history books, even US history books. The present may be cloudy, but the 1940s are less so - listen to their hawkish views, then consider how clear their view of history is.
So Russia almost certainly could have rolled into Finland in 1945.